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What's the difference between a gateway and a router?@Eugene: The diagramming style is based on classic 10-Base-2 Ethernet diagramming style. Regard it as symbolic. All devices attached to a horizontal line are linked by an Ethernet switch (or hub, it doesn't affect the answer). Server knows 60.20.60.99 is on a different subnet (by comparing addresses after applying the netmask) so it looks in it's routing table to find a route. It probably only has a default route for R1 so it assembles a packet with data for 60.20.60.99 with the MAC address of R1. R1 receives the packet and consult's its own routing tables & forwards the packet to R2, Repeat.

Access to a network server without port forwarding@SdevDavid: Searching by the listening port on the Android device means you don't see any set-up traffic between device and router (or external service) prior to the establishment of an inbound TCP connection.

Jun12

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Access to a network server without port forwarding@SevDavid: To find out what your WiFi IP-camera does, you'd need an 802.11 sniffer. Or plug it into an intermediary Ethernet switch that has port-mirroring (or use a hub). But see IGDP in updated answer.